PARTS AND SERVICE MANUAL FOR MERCO HOLDING CABINET MODEL 86002 Merco Savory, Inc. 1111 North Hadley Road Fort Wayne, Indiana 46804 United States of America Phone: (260) 459-8200 U.S. Facsimile: (888) 790-8193 Int l Facsimile: (260) 436-0735 Service Hotline: (800) 678-9511 www.mercosavory.com MHCservmanual REV: B
SPECIFICATIONS TOP VIEW FRONT VIEW SIDE VIEW Model # Voltage Amps Watts Hz. Net Wt. lbs./kg Plug 86002 120 10.4 1250 60 30/14 6 Nema 5-15P 2 Holding Cabinet Service Manual
MHC-22-GEN CONTROL PANEL MODEL 86002 Bin Button #1 Bin Button #2 Up Arrow Button Program Button Down Arrow Button Temperature Button Time Button Bin Button #3 Bin Button #4 Holding Cabinet Service Manual 3
WIRING DIAGRAM 4 Holding Cabinet Service Manual
SEQUENCE OF OPERATION Power Supply Electrical power is supplied to the unit by a 3 conductor service for single phase. 120VAC Black conductor is hot. White conductor is neutral. Green and yellow conductor is ground. Power is permanently supplied to the main power switch. Heating Circuit Closing the main power switch supplies voltage to the power board and user interface. Temperature is set through the user interface which then intermittently supplies 120VAC to the heater plates. Temperature is then controlled by the thermocouples sending a reference signal back to the user interface. Holding Cabinet Service Manual 5
TROUBLESHOOTING GUIDE SYMPTOM POSSIBLE CAUSE EVALUATION Holding Cabinet will not heat Incoming Power Supply Verify power cord is secured firmly in receptacle. Measure the incoming voltage. Check circuit breakers. Reset if required. Call power company if needed. Power Switch Check continuity between switch terminals. Replace switch as needed. Unit doesn t reach desired temperature Temperature is too high Thermocouple Heat Element Thermocouple Heat Element Check for continuity in circuit. Compare cavity temperature with display reading. Insert temperature probe into center of cavity. Acceptable temperature variation is +/- 20 from display reading. Check for loose connection. Check the Amp draw on each element for proper load. Check page 2 for rating information. If the amp draw is high or low, check the individual elements for opens, shorts and proper resistance. WITH POWER OFF: To check resistance of the elements, remove all leads from the elements and use a digital multimeter. The element resistance should be as follows: 120V 87 ohms Replace heating element (shelf) as needed. Check thermostat (common wire). Please note that if thermostat is bad, both circuits will be bad. Check for incorrectly wired thermocouple. Thermocouple wire polarities are reversed. Compare cavity temperature with display reading. Insert temperature probe into center of cavity. Acceptable temperature variation is +/- 20 from display reading. Check for loose connection. Check the Amp draw on each element for proper load. Check page 2 for rating information. If the amp draw is high or low, check the individual elements for opens, shorts and proper resistance. WITH POWER OFF: To check resistance of the elements, remove all leads from the elements and use a digital multimeter. The element resistance should be as follows: 120V 87 ohms Replace heating element (shelf) as needed. 6 Holding Cabinet Service Manual
TROUBLESHOOTING GUIDE (CONT D) Display reads unusual characters On/Off switch doesn t light (but unit works properly) Power Switch Make sure wires are connected properly (grounded). If wires are grounded properly, new control board is needed. Check wiring to switch. HEAT SHELF REPLACEMENT 1. Disconnect power. 2. Take out screws holding L Brackets in cavity. 3. Disconnect thermocouple and all power connections to board. Mark all wires for reassembly. 4. Take out power board. 5. Take out shelf mounting screws from both sides. 6. Remove shelves and feed wiring out of unit.! WARNING: Be careful to avoid tearing the aluminum foil while working with wire connections. 7. Reassemble in reverse order. USER INTERFACE (U.I.) BOARD REPLACEMENT 1. Remove four (4) screws. 2. Disconnect thermocouples. 3. Disconnect ribbon cable. 4. Remove board. 5. Reassemble in reverse order.! When replacing U.I. board, be sure ribbon cable is connected so that blue wire is facing towards interior of unit. Holding Cabinet Service Manual 7
PARTS BREAKDOWN LABEL PART NUMBER PART DESCRIPTION A 340040 Back Panel Assembly B 340041 Side Panel C 340042 Power Board Assembly D 340043 Controller, User Interface E 340038 Switch, Rocker, Lighted F 10000949 Overlay, Control Panel G 340045 Bracket, Heater Side H 340046 Tray Seal I 340011 Leg J 340015 Tray, Plastic K 340025 Tray Cover, Front Retention Rod, Assembly L 10000968 Side Insulation M 340048 Top / Bottom Insulation N 10000966 Heater Insulation O 10000946-02 Lower Shelf Assembly** P 340051 Upper-Upper Shelf Assembly** Q 340052 Lower-Upper Shelf Assembly** R 340053 Rod, Rear Tray Seal Retainer S 000171 Strain Relief Not Shown 340054 Power Cord, NEMA 5-15P Not Shown 340055 Ribbon Cable (Power Board to Interface) Not Shown 340056 Cable (On / Off Switch to Power Board) Not Shown 340017 Retention Rod Spring Not Shown 340014 Retention Rod Spring Clip 8 Holding Cabinet Service Manual
GENERAL VIEW Holding Cabinet Service Manual 9
DIAGNOSTIC MODE Press and hold down the Temperature button until you hear a short, double-beep sound. In this mode all displays indicate temperatures for either the upper or lower heaters for each bin. Pressing the Up and Down arrow buttons will select the upper and lower heaters respectively. In this mode, pressing the Time button will also display the PWM output power duty cycle. This is shown as a percent for the corresponding heater. The thermocouple calibration system can only be accessed from within the diagnostic mode. THERMOCOUPLE CALIBRATION SYSTEM Make sure heater zone to be calibrated is at temperature and stable. Measure actual temperature and proceed with following procedure. Enter Diagnostic Mode by pressing and holding down the Temperature button. After a second or so, the actual temperatures as measured by holding cabinet are displayed. Use Up or Down buttons to select either the upper or lower heating zone for each bin. Press Bin select button to select bin containing heating zone to be calibrated. Note: Bin display will alternate between showing temperature and calibration offset. As the calibration offset is changed the temperature displayed will reflect this. Use the Up and Down buttons to make the displayed temperature match the actual temperature as independently measured. To apply the temperature calibration correctly, press and hold the Temperature button down. While pressing the Temperature button, press Program button (for 1 second) until the unit beeps. Once program in completed the temperature correction is applied and the heater zone will adjust its temperature. The user interface returns to the actual temperature display. Once a bin is selected for programming, if no keys are entered for 10 seconds the calibration mode is terminated and the display returns to actual temperature display mode. THERMOCOUPLE FAULT DETECTION The thermocouple (TC) fault detection logic is disabled for 10 minutes following initial power application. This allows time for all heating zones to develop enough heat to not trigger a shorted thermocouple fault. 10 Holding Cabinet Service Manual
THERMOCOUPLE FAULT DETECTION (CONT D) If a fault is detected in any bin, the display for that bin will show ErNN where NN is a numeric error code. This two digit error code uses the first digit for the upper heater zone. If a short is detected, the digit will be a 1, if an open is detected a 2 will be displayed. If the heater zone is operating properly, a 0 will be displayed. ErNN UPPER HEATER ZONE LOWER HEATER ZONE Some Examples: Er01 Indicates Upper heater zone is good. Lower heater zone TC short detected. Er02 Indicates Upper heater zone is good. Lower heater zone TC open detected. Er10 Indicates Upper heater zone TC short detected. Lower heater zone is good. Er20 Indicates Upper heater zone TC open detected. Lower heater zone is good. Er22 Indicates Upper and Lower heater zone TC s detected open. Cold Indicates Temperature of heater zone is below set point. Hot Indicates Temperature of heater zone is above set point. Once and error is indicated for a heater zone the affected heater is shut off. The only way to clear an error indication is by cycling the power off then on again. To reset the holding bin controller to the factory configuration, hold down the upper-left Bin button while powering on the controller. Release the Bin button as soon as the displays illuminate. This resets the following settings: All product names Upper and lower temperature for each product Expiration and Cook More time for each product NOTE: For additional information concerning Menu and Product programming, please refer to Merco Holding Cabinet Installation & Operation Manual. Holding Cabinet Service Manual 11
Merco Savory, LLC 1111 North Hadley Road Fort Wayne, Indiana 46804 United States of America Telephone: (260) 459-8200 U.S. Facsimile: (888) 790-8193 Int l Facsimile: (260) 436-0735 Service Hotline: (800) 678-9511 www.mercosavory.com 12 Holding Cabinet Service Manual